TYC9486-927-1 Star System: Largest Solar System Ever Discovered?

Labeled as a “rogue planet” when it was discovered eight years ago, does the exoplanet 2MASSJ2126-8140 and its parent star TYC9486-927-1 make up the largest solar system discovered so far? 

By: Ringo Bones 

When it was first discovered and observed by astronomers eight years ago, the exoplanet 2MASSJ2126-8140 was first thought of as a “rogue planet” – i.e. a planet ejected away from its parent star and destined to wander forever across the universe because it doesn’t seem to orbit any star. But after a few years of careful observation, it was then found out that this exoplanet is part of the largest solar system discovered so far. 

Exoplanet 2MASSJ2126-8140, a gas giant type planet, was recently found out to lie one million kilometers away from its parent star TYC9486-927-1 which makes its orbit 140 times wider than Pluto’s orbital path around our Sun. Only a handful of extremely wide pairs of this kind have been found in recent years. Details were published in the Monthly Notices of the Royal Astronomical Society back in January 27, 2016. 

Exoplanet 2MASSJ2126-8140 has an observed mass between 12 to 15 times that of the planet Jupiter.  

Exoplanet 2MASSJ2126-8140’s distance from its parent star is around 7,000 times the distance between Earth and the Sun and about 140 times the distance between Pluto and the Sun. This makes it the widest of any planet around a star discovered so far by a significant margin – about three times the width of the previously widest pair discovered. If it orbited around our Sun, exoplanet 2MASSJ2126-8140 would lie far beyond Pluto – like approximately in the midst of our Solar System’s Oort Cloud. 

That huge gap – which equals to 6,900 Astronomical Units (AU) – means it would take exoplanet 2MASSJ2126-8140 about 900,000 years to complete a single orbit around its parent star TYC9486-927-1. By estimating the parent star’s age using its lithium signature, the researchers say TYC9486-927-1 is somewhere between 10 million and 45 million years old. This would mean that exoplanet 2MASSJ2126-8140 has completed less than 50 orbits around its parent star since coalescing from the primordial gas and dust from which it first came.